Credit: NASA.

The planet is already 1°C warmer than it was prior to the Industrial Revolution during the mid-19th century. Many experts believe this rapid warming is responsible for the streak of droughts, floods, heat waves, and other extreme weather patterns observed in the past decade. By the end of the century, if current greenhouse gas emission trends continue unabated, the planet is expected to warm by at least 3°C, possibly 5°C, according to the IPCC.

Playing with the weather

Given the potentially catastrophic outcomes of such a scenario, many scientists have proposed geoengineering the planet by spraying sunlight-blocking aerosols into the atmosphere to produce an artificial cooling effect. A new study, however, suggests that if that happens, there is little room to turn back since abruptly canceling geoengineering could have devastating consequences for wildlife.

Perhaps the most commonly available geoengineering method at our disposal is simply to plant more trees, preferably to replace those we’ve cut down but also planting new forests where none were to begin with. After these trees die, however, it’s important we dispose of the carbon they consumed over their lifetimes. One solution is to transform the trees into biochar — turning trees into charcoal essentially — then burying it somewhere.

Geoengineering — also called radiation management — in the context explored by University of Maryland researchers, involves injecting billions of tiny particles into the upper atmosphere (stratosphere) which bounce light back into space, thereby cooling the planet. Some of these aerosols include sulfur-based compounds, which the public often finds very undesirable.

Last year, at COP22 Marrakech, I had heard Prof. Peter Wadhams from Cambridge University say that we can just as well help clouds become whiter by injecting benign water vapor particles at the level of the stratocloud, the lowest level at which clouds form. As a result, the finely divided water particles form salt crystals that stay suspended and gray clouds become whiter. We would use planes, hot-air balloons and even suspended pipes to inject the aerosols into the stratosphere.

If anything, scientists are merely taking cues from natural cooling processes like volcanism. For instance, the 1991 Mount Pinatubo eruption spewed 15 million tons of sulfur dioxide into the stratosphere, which cooled the planet by 0.5 °C, on average, for about two years.

To be clear, geoengineering is a last-resort solution. The problem is that we don’t know much about geoengineering since it has never been attempted on the kind of scale that would be required to alter the planet’s climate, for very obvious reasons.

This means that scientists don’t actually know if it will work in the first place, which is why some experts like Prof. Wadhams have called for immediate research. He reasons that when push comes to shove, we should at least know whether or not spraying aerosols in the atmosphere works, rather than relying on the practice as an extreme, unproven solution. And if geoengineering works at the start, we might never be able to put the brakes on it.

Once on this path, there’s no turning back

Prof. Christopher Trisos and colleagues at the University of Maryland studied a scenario where five million tons of sulfur dioxide per year are sprayed into the stratosphere over a period of 50 years, from 2020 to 2070. Under this assumed scenario, while the world is reducing its carbon emissions, the planet would cool down by about 1°C, thereby resetting temperature to pre-Industrial levels.

However, what Trisos’ team found is that abruptly switching off geoengineering would lead to temperature increase at a rate ten times faster than had geoengineering never been deployed. The analysis suggests that many creatures, be they plants or animals, would be overwhelmed by the all too sudden warming weather patterns. Particularly, the researchers found, amphibians and land animals would be unable to migrate quickly enough to escape or adapt elsewhere. What’s more, the sudden change in temperature and weather means that migrating in one direction may imply cooler conditions but not necessarily the right rainfall, and vice-versa.

“Rapid geoengineering termination would significantly increase the threats to biodiversity from climate change,” the authors wrote.

This scenario isn’t that far-fetched. It’s quite plausible that some countries would become very angry about geoengineering and would demand it stops, maybe threatening with war.

“Imagine large droughts or floods around the world that could be blamed on geoengineering, and demands that it stop. Can we ever risk that?” co-author Alan Robock of the Department of Environmental Sciences at Rutgers University-New Brunswick, told Reuters. 

“If geoengineering ever stopped abruptly, it would be devastating. So you would have to be sure that it could be stopped gradually, and it is easy to think of scenarios that would prevent that,” he added.

The findings published in the journal Nature Ecology & Evolution first and foremost assume a scenario where radiation management on a planetary scale actually works. For now, this is an unproven concept, and it’s bugging many scientists.

“If solar radiation management is unworkable, we need to know now,” commented Ben Kravitz, a climate scientist at Pacific Northwest National Laboratory in Washington and an expert on geoengineering.

“What terrifies me is that people are going to start relying on it, and then we find out later that it is not going to work and we are already locked in,” he told the AFP.

A team from Harvard plans on conducting preliminary atmospheric tests in the Arizona desert this fall. But, it will still take years before we’ll know with a fair degree of confidence whether or not geoengineering works. Until then, we should not count on this very extreme solution to solve the climate change problem. Geoengineering, if it ever comes to that, will always be a temporary solution because it doesn’t solve the root problem. All that CO2 is still there, and when the atmosphere clears, it will be ready to soak up all of that infrared radiation and warm the planet. So, it’s up to each and every one of us to take urgent action — the only sustainable solution is to dramatically reduce greenhouse gas emissions.